Stamping apparatus and stamping method

ABSTRACT

A stamping apparatus includes a die, a punch, a back-pressure device, a lift-up mechanism, and a delay device. A workpiece is mounted on the die. The punch is arranged to approach and recede from the die and configured to punch out a product from the workpiece. The back-pressure device includes a pushing member disposed in the die and urges the pushing member toward the punch to apply back pressure to the workpiece. The lift-up mechanism is configured to lift the workpiece above the die when the punch recedes from the die. The delay device is configured to delay lifting movement of the pushing member in relation to receding movement of the punch when the punch recedes from the die.

BACKGROUND 1. Field

The following description relates to a stamping apparatus and a stamping method.

2. Description of Related Art

Japanese Laid-Open Patent Publication No. 2003-117619 discloses a method for stamping a product having teeth on the outer circumference, in which a material is first pressed so that an intermediate product, the perimeter of which is connected to the material, is half-blanked. At the same time, pressure is applied to a central portion of the intermediate product to move the central portion toward the perimeter. Then, the intermediate product is forced back toward the material so that the perimeter of the intermediate product is detached from the material. Finally, the intermediate product is removed from the material, and the central portion of the intermediate product is punched out. As a result, the product is formed.

When stamping a product that requires accuracy in the sheared surface, a number of processing steps is performed to ensure the accuracy. Such a method is burdensome.

SUMMARY

It is an objective of the present disclosure to provide a stamping apparatus and a stamping method that increase productivity.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In one general aspect, a stamping apparatus includes a die on which a workpiece is mounted, a punch arranged to approach and recede from the die and configured to punch out a product from the workpiece, a back-pressure device including a pushing member disposed in the die, the back-pressure device urging the pushing member toward the punch to apply back pressure to the workpiece, a lift-up mechanism configured to lift the workpiece above the die when the punch recedes from the die, and a delay device configured to delay lifting movement of the pushing member in relation to receding movement of the punch when the punch recedes from the die.

In another general aspect, a stamping method includes, when punching out a product from a workpiece by causing a punch to approach and recede from a die on which the workpiece is mounted, applying back pressure to the workpiece from a side opposite to the punch using a pushing member, and when the punch recedes from the die, lifting the workpiece above the die and delaying lifting movement of the pushing member in relation to receding movement of the punch.

Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a stamping apparatus and a stamping method according to an embodiment, illustrating the structure of the stamping apparatus.

FIG. 2 is a perspective view of a back-pressure device and a delay device of the embodiment of FIG. 1.

FIG. 3 is a cross-sectional view of an upper die assembly of the embodiment in which section A shows a cross section that differs from that in FIG. 1.

FIG. 4A is a bottom view of a switch member from a side of a rotation plate when the rotation plate is located in an opposing position.

FIG. 4B is a bottom view of the switch member from a side of the rotation plate when the rotation plate is located in an accommodated position.

FIG. 5 is a cross-sectional view of the stamping method of the embodiment of FIG. 1, illustrating a state in which upper pins are in contact with lower pins.

FIG. 6 is a cross-sectional view of the stamping method of the embodiment of FIG. 1, illustrating a state in which the upper ends of the upper pins are accommodated in recesses of the switch member.

FIG. 7 is a cross-sectional view of the stamping method of the embodiment of FIG. 1, illustrating a state in which a metal core is inserted into a through hole of a workpiece.

FIG. 8 is a cross-sectional view of the stamping method of the embodiment of FIG. 1, illustrating a state in which a product is punched out from the workpiece by a punch.

FIG. 9 is a cross-sectional view of the stamping method of the embodiment of FIG. 1, illustrating a state in which the rotation plate is switched from the accommodated position to the opposing position.

FIG. 10 is a cross-sectional view of the stamping method of the embodiment of FIG. 1, illustrating a state in which the metal core is receded from the through hole of the workpiece.

FIG. 11 is a cross-sectional view of the stamping method of the embodiment of FIG. 1, illustrating a state in which the punch is receded from the workpiece.

FIG. 12 is a cross-sectional view of the stamping method of the embodiment of FIG. 1, illustrating a state in which the product is lifted by a lifter.

Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

This description provides a comprehensive understanding of the methods, apparatuses, and/or systems described. Modifications and equivalents of the methods, apparatuses, and/or systems described are apparent to one of ordinary skill in the art. Sequences of operations are exemplary, and may be changed as apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted.

Exemplary embodiments may have different forms, and are not limited to the examples described. However, the examples described are thorough and complete, and convey the full scope of the disclosure to one of ordinary skill in the art.

A stamping apparatus and a stamping method according to an embodiment will now be described with reference to FIGS. 1 to 12.

As shown in FIG. 1, the present embodiment of a stamping apparatus 10 is configured to punch out a product P from a plate-shaped workpiece 200, which is conveyed from right to left in FIG. 1. The product P of the present embodiment is a gear having teeth on the outer circumference. In the description hereafter, the conveying direction of the workpiece 200 (sideward direction in FIG. 1) is referred to as a conveying direction X.

The stamping apparatus 10 includes a lower die assembly 20 including a die 25 and an upper die assembly 50 including a punch 70. The workpiece 200 is conveyed and mounted on the die 25. The punch 70 is arranged to approach and recede from the die 25 in the vertical direction and configured to punch out the produce P from the workpiece 200. The upper die assembly 50 is coupled to a slider (not shown) that reciprocates in the vertical direction and is arranged to approach and recede from the lower die assembly 20.

The structure of the lower die assembly 20 will now be described.

Lower Die Assembly 20

As shown in FIG. 1, the lower die assembly 20 includes a die holder 22 disposed on a base 21 and a die plate 23 fixed to an upper portion of the die holder 22 to accommodate the die 25. The die 25 has a gear forming portion on the inner circumferential surface.

Multiple (five, in the present embodiment) gas cylinders 31 (urging portions) are arranged in the die holder 22 and fixed to the base 21. Each of the gas cylinders 31 includes a cylinder 31 a and a piston rod 31 b configured to reciprocate in the cylinder 31 a. The piston rod 31 b projects upward. The space defined by the cylinder 31 a and the piston rod 31 b is filled with gas such as nitrogen. The piston rod 31 b is urged upward by the pressure of the gas in the cylinder 31 a.

As shown in FIGS. 1 and 2, an intermediate portion 32 is plate-shaped and rhombic in a plan view and is coupled to the distal ends of the piston rods 31 b of the gas cylinders 31. The intermediate portion 32 is urged upward by the gas cylinders 31 and is in contact with the lower surface of the die plate 23.

Multiple (six, in the present embodiment) support pins 33 project from a central portion of the intermediate portion 32 in the conveying direction X. The support pins 33 are inserted through respective through holes 23 a formed in the die plate 23. The upper ends of the support pins 33 are located in the die 25.

The upper ends of the support pins 33 are coupled to a discoid base plate 34 disposed in the die 25.

A pushing member 35 is disposed on the upper surface of the base plate 34. The pushing member 35 has a center hole 35 a and a gear forming portion on the outer circumferential surface. The center hole 35 a is a stepped hole in which a lower part has a larger diameter than an upper part.

In the present embodiment, the gas cylinders 31, the intermediate portion 32, the support pins 33, the base plate 34, and the pushing member 35 configure a back-pressure device 30. The back-pressure device 30 urges the pushing member 35 toward the punch 70 using the gas cylinders 31 to apply back pressure to the workpiece 200.

As shown in FIG. 1, a lifter 37 is disposed in the center hole 35 a of the pushing member 35 and urged by a compression spring 36 toward the punch 70 so that the lifter 37 retractably extends from the pushing member 35. The lifter 37 has a cylindrical shape with a lower open end and a closed upper end, defining a recess 37 a. The upper and lower ends of the compression spring 36 are coupled to the closed end surface of the recess 37 a of the lifter 37 and the upper surface of the base plate 34, respectively. A flange projects circumferentially outward from the lower end of the lifter 37 along the entire perimeter. The flange is in contact with the step in the center hole 35 a of the pushing member 35 to stop removal of the lifter 37 from the pushing member 35.

Two through holes 23 b vertically extend through the die plate 23 at opposite sides of the die 25 in the conveying direction X. Each through hole 23 b receives a lower pin 24. The lower end of each lower pin 24 is opposed to the upper surface of the intermediate portion 32. More specifically, the lower pins 24 are disposed at opposite sides of the intermediate portion 32 in the conveying direction X (refer to FIG. 2). In the present embodiment, the lower pins 24 are coupled to the upper surface of the intermediate portion 32. Therefore, the lower pins 24 are movable in the vertical direction in accordance with reciprocation of the piston rods 31 b of the gas cylinders 31. When the intermediate portion 32 is in contact with the lower surface of the die plate 23, the upper ends of the lower pins 24 project from the upper surface of the die plate 23.

A lift-up mechanism 40 is arranged on an upstream side (left side in FIG. 1) of the lower die assembly 20 in the conveying direction X. The lift-up mechanism 40 is configured to lift the workpiece 200 above the die 25 when the punch 70 recedes from the die 25, and more specifically, when the upper die assembly 50 recedes from the lower die assembly 20. The lift-up mechanism 40 includes a base 41 coupled to the lower die assembly 20 and a clamp 43 clamping the workpiece 200 in the vertical direction. The base 41 includes a receptacle 42 that is open upward. A compression spring 44 is disposed in the receptacle 42. The clamp 43 is urged upward by the compression spring 44 disposed in the receptacle 42.

The structure of the upper die assembly 50 will now be described.

Upper Die Assembly 50

The upper die assembly 50 includes a top plate 51, a housing 52, a punch holder 80, and a stripper backing 90. The housing 52 is fixed to the lower surface of the top plate 51 and accommodates a gas cylinder 60. The punch holder 80 holds the punch 70. The stripper backing 90 presses the workpiece 200 onto the lower die assembly 20 and guides the punch 70 in the vertical direction. The gas cylinder 60 and the gas cylinders 31 have the same structure.

The structure of the punch 70 will now be described in detail.

Punch 70

The punch 70 is opposed to the pushing member 35. The punch 70 has a gear forming portion on the outer circumferential surface. A through hole 70 a vertically extends through a center portion of the punch 70. A metal core 71 is inserted through the through hole 70 a to extend vertically. The upper end of the metal core 71 is fixed to the punch holder 80.

In the present embodiment, in a step prior to the step of punching out the product P using the stamping apparatus 10, a through hole 201 is formed in a portion of the workpiece 200 that is to be punched out by the punch 70. When punching out the product P, the metal core 71 is inserted through the through hole 201. This limits deformation of the through hole 201 and allows the punch 70 to stably punch out the product P from the workpiece 200. The through hole 201 has a smaller diameter than the lifter 37.

Two holding pins 72 are disposed in opposite sides of the punch 70 in the conveying direction X to retractably extend from the lower surface of the punch 70. The holding pins 72 are urged downward by compression springs 73 disposed in the punch 70. The sum of urging forces of the holding pins 72 is greater than urging force of the lifter 37.

Punch Holder 80

The punch holder 80 is coupled to a lower portion of the housing 52.

The punch holder 80 includes an accommodation recess 80 a that is open downward to accommodate the upper end of the punch 70. The accommodation recess 80 a has an upper surface including multiple (two, in the present embodiment) through holes 80 b vertically extending through the punch holder 80.

A pressing pin 53 is inserted through each of the through holes 80 b. The upper end of each pressing pin 53 extends through the lower portion of the housing 52 and is coupled to the gas cylinder 60 in the housing 52. The lower end of each pressing pin 53 is coupled to the upper end of the punch 70.

The punch holder 80 is vertically movable relative to the punch 70. When the punch holder 80 vertically moves relative to the punch 70, the metal core 71 fixed to the punch holder 80 extends from the lower surface of the punch 70.

Two through holes 80 c vertically extend through the punch holder 80 at opposite sides of the punch holder 80 in the conveying direction X. Each through hole 80 c is a stepped hole in which a lower part has a larger diameter than an upper part. Each through hole 80 c receives an upper pin 81 so that the upper pin 81 is movable in the vertical direction. The upper pins 81 are coaxial with the lower pins 24 of the lower die assembly 20. Each upper pin 81 has a vertically-central portion having a larger diameter than the other portion, defining an enlarged portion 81 a. The portion of the upper pin 81 located below the enlarged portion 81 a is inserted through a through hole 90 c, which extends through the stripper backing 90. A compression spring 82 is disposed between the upper end of the enlarged portion 81 a of each upper pin 81 and the stepped portion of the corresponding through hole 80 c. The upper pins 81 are urged downward by the compression springs 82 to retractably extend from the lower surface of the stripper backing 90. In addition, when the lower end of the enlarged portion 81 a of each upper pin 81 contacts the upper surface of the stripper backing 90, downward movement of the upper pin 81 is restricted. Vertical movement of the upper die assembly 50 allows the lower ends of the upper pins 81 to contact and separate from the upper ends of the lower pins 24.

In the present embodiment, in a step prior to the step of stamping the product P with the stamping apparatus 10, through holes 202 are formed in portions of the workpiece 200 that are opposed to the lower pins 24 and the upper pins 81 so that the lower pins 24 and the upper pins 81 are inserted through the through holes 202.

Stripper Backing 90

A punch guide hole 90 a is formed in a central portion of the stripper backing 90 in the conveying direction X to guide the punch 70. The lower surface of the stripper backing 90 includes an accommodation recess 90 b, which is connected to the punch guide hole 90 a.

A stripper plate 91 is accommodated in the accommodation recess 90 b to push the workpiece 200, mounted on the die 25, from above. The lower surface of the stripper plate 91 is substantially flush with the lower surface of the stripper backing 90.

A punch guide hole 91 a is formed in a central portion of the stripper plate 91 in the conveying direction X to guide the punch 70.

The stripper backing 90 is coupled to a gas cylinder 61 by a coupling member 92. The gas cylinder 61 is fixed to an upstream side of the lower surface of the top plate 51 in the conveying direction X. The coupling member 92 extends through the punch holder 80. The gas cylinder 61 and the gas cylinders 31 have the same structure.

The lower surface of the stripper backing 90 has an upstream portion in the conveying direction X including an escape portion 93. When the upper die assembly 50 is lowered, the escape portion 93 accommodates the upper portion of the clamp 43 of the lift-up mechanism 40.

Switch Member 100

A cylindrical switch member 100 is disposed above the punch holder 80 to be rotational about an axis C extending vertically. The switch member 100 includes a base 102 and a rotation plate 103. The rotation plate 103 is disposed on the lower surface of the base 102 to be rotational relative to the base 102 and has an opposing surface 104 opposed to the upper ends of the upper pins 81. The switch member 100 has a central portion including a center hole 101 that vertically extends through the base 102 and the rotation plate 103.

The lower portion of the housing 52, which is fixed to the top plate 51, is located in the center hole 101 of the switch member 100. The switch member 100 is movable relative to the housing 52 in the vertical direction.

The upper surface of the base 102 is urged downward by multiple (eight, in the present embodiment) gas cylinders 62, which are fixed to the lower surface of the top plate 51. The gas cylinders 62 are disposed at intervals in the circumferential direction about the axis C. The gas cylinders 62 and the gas cylinders 31 have the same structure.

As shown in FIGS. 1, 4A, and 4B, two recesses 105 are formed in portions of the opposing surface 104 of the rotation plate 103 to accommodate the upper ends of the upper pins 81.

As shown in FIGS. 4A and 4B, the recesses 105 are elongated holes radially extending about the axis C. The recesses 105 extend through the rotation plate 103.

Multiple (four, in the present embodiment) receiving holes 106 are formed in the opposing surface 104 of the rotation plate 103 at equal intervals in the circumferential direction. The receiving holes 106, which are elongated holes extending in the circumferential direction about the axis C, extend through the rotation plate 103.

As shown in FIG. 3 with section A, a through hole 80 d is formed in the punch holder 80 in a portion corresponding to each receiving hole 106. Four support rods 94 project from the upper surface of the stripper backing 90 and are inserted through the through holes 80 d. The upper end of each support rod 94 is coupled to the lower surface of the base 102 in the corresponding receiving hole 106. The support rods 94 maintain a fixed vertical distance between the stripper backing 90 and the switch member 100. For the sake of convenience, in FIG. 3, section A shows a cross section of one of the support rods 94 and one of the receiving holes 106 of the upper die assembly 50. This cross section differs from the portion shown in in FIG. 1.

As shown in FIGS. 4A and 4B, the receiving holes 106 are elongated holes extending in the circumferential direction. Thus, when the support rods 94 are accommodated in the receiving holes 106, rotation of the rotation plate 103 is allowed.

The rotation plate 103 has a circumferential portion on which a gear portion 107 is formed.

Drive Mechanism 110

As shown in FIGS. 2, 4A, and 4B, the upper die assembly 50 includes a drive mechanism 110 configured to rotate the rotation plate 103 about the axis C. The drive mechanism 110 includes an elongated slide bar 111 extending in the conveying direction X and an air cylinder 113 that reciprocates the slide bar 111 in the conveying direction X.

The proximal end of the slide bar 111 is coupled to an output shaft 114 of the air cylinder 113. A gear portion 112 is formed on a portion of the distal end of the slide bar 111 opposed to the rotation plate 103 to engage the gear portion 107 of the rotation plate 103. Reciprocation of the slide bar 111 in the conveying direction X rotates the rotation plate 103 about the axis C.

As shown in FIGS. 4A and 4B, the drive mechanism 110 switches the position of the rotation plate 103 between an opposing position in which the upper ends of the upper pins 81 are opposed to the opposing surface 104 and an accommodated position in which the upper ends are accommodated in the recesses 105.

When the support rods 94 of the stripper backing 90 are accommodated in the receiving holes 106 of the rotation plate 103, the position of the rotation plate 103 is switchable between the opposing position and the accommodated position.

In the present embodiment, the lower pins 24 of the lower die assembly 20, the upper pins 81 of the upper die assembly 50, the switch member 100, and the drive mechanism 110 configure a delay device 120. The delay device 120 is configured to restrict upward movement of the intermediate portion 32, thereby delaying lifting movement of the pushing member 35 in relation to receding movement of the punch 70, during a set period from when the punch 70 starts to retract from the die 25.

The stamping method of punching out the product P from the workpiece 200 using the stamping apparatus 10 will now be described.

As shown in FIG. 1, the workpiece 200 is conveyed and placed between the lower die assembly 20 and the upper die assembly 50. At this time, the workpiece 200 is held by the clamp 43 of the lift-up mechanism 40 at a position separated upward from the lower die assembly 20. The position of the rotation plate 103 of the switch member 100 is set to the accommodated position. In addition, the upper end of the punch 70 is spaced apart by a gap from the upper surface of the accommodation recess 80 a of the punch holder 80.

Then, the slider (not shown) presses the top plate 51 of the upper die assembly 50 to lower the upper die assembly 50 toward the lower die assembly 20 and bring the stripper backing 90 into contact with the upper surface of the workpiece 200.

At this time, the holding pins 72 of the punch 70 are in contact with the upper surface of the workpiece 200 and recede in the punch 70. The upper pins 81 are inserted into the through holes 202 of the workpiece 200. The upper portion of the clamp 43 of the lift-up mechanism 40 is received in the escape portion 93 of the stripper backing 90.

As shown in FIG. 5, the upper die assembly 50 is further lowered, so that the upper ends of the lower pins 24 come into contact with the lower ends of the upper pins 81. At this time, the clamp 43 moves downward against the urging force of the compression spring 44.

As shown in FIG. 6, when the upper die assembly 50 is further lowered, the lower surface of the workpiece 200 comes into contact with the upper surface of the die 25. As a result, the lifter 37 is forced downward and is entirely accommodated in the pushing member 35.

In the state shown in FIG. 5, the upper pins 81, which are accommodated in the punch holder 80 and movable in the vertical direction, are in contact with the lower pins 24. Thus, downward movement of the upper pins 81 is restricted. In this state, the upper die assembly 50 is lowered. As a result, the components of the upper die assembly 50 excluding the upper pins 81 are moved downward relative to the upper pins 81. As described above, since the position of the switch member 100 is set to the accommodated position, when the upper die assembly 50 is lowered, the upper ends of the upper pins 81 are received in the recesses 105 of the switch member 100 (refer to FIG. 6).

In this state, the workpiece 200 is held between the upper die assembly 50 and the lower die assembly 20, so that downward movement of the stripper backing 90 is restricted.

In the description hereafter, the vertical position of the punch 70 in this state is referred to as a preparation position. The preparation position corresponds to a set position of the present disclosure. When the punch 70 is located in the preparation position, the upper surface of the punch holder 80 is in contact with the opposing surface 104 of the rotation plate 103.

As shown in FIG. 3, the coupling member 92 is disposed between the gas cylinder 61 and the stripper backing 90. The switch member 100 and the support rods 94 are disposed between the stripper backing 90 and the gas cylinders 62. In addition, as described above, the switch member 100 is vertically movable relative to the housing 52, which is fixed to the top plate 51.

Therefore, as shown in FIG. 7, when the top plate 51 is pressed by the slider, the top plate 51 is moved downward as the piston rods of the gas cylinder 61 and the gas cylinders 62 are retracted. At the same time, the punch holder 80 is pressed downward by the housing 52. Since the coupling member 92 and the support rods 94 are inserted through the punch holder 80, the punch holder 80 is moved downward together with the top plate 51 and the housing 52.

As described above, when downward movement of the stripper backing 90 is restricted and the punch holder 80 is moved downward together with the top plate 51 and the housing 52, the switch member 100 will not move downward in a stroke range in which the piston rods of the gas cylinder 61 and the gas cylinders 62 are retractable.

As described above, when the housing 52 and the punch holder 80 are moved downward together with the top plate 51, the punch 70 is in contact with the workpiece 200, so that downward movement of the punch 70 is restricted. The upper end of the punch 70 is coupled by the pressing pins 53 to the gas cylinder 60 in the housing 52. When the top plate 51 is pressed by the slider, the top plate 51 is moved downward together with the housing 52 and the punch holder 80 as the piston rod of the gas cylinder 60 is retracted.

As a result, the metal core 71, which is fixed to the punch holder 80, projects from the lower surface of the punch 70 and is inserted into the through hole 201 of the workpiece 200. At this time, the gap between the upper end of the punch 70 and the upper surface of the accommodation recess 80 a of the punch holder 80 is filled.

As shown in FIG. 8, the top plate 51 is further pressed by the slider to lower the punch 70 to the bottom dead center. As the back-pressure device 30 applies back pressure to the workpiece 200, the product P is punched out from the workpiece 200. The bottom dead center of the punch 70 is a position where the lower surface of the punch 70 is slightly below the upper surface of the die 25, that is, the lower surface of the workpiece 200. Therefore, the workpiece 200 is spaced apart from the product P by a slight gap in the vertical direction.

At this time, the back-pressure device 30 is pressed downward by the punch 70 and thus is moved downward. Accordingly, the upper ends of the upper pins 81, which are urged downward by the compression springs 82, are removed from the recesses 105 of the switch member 100.

Then, as shown in FIG. 9, the drive mechanism 110 is driven to set the position of the rotation plate 103 of the switch member 100 to the opposing position. As a result, the upper pins 81 and the lower pins 24, which are in contact with each other, are held between the opposing surface 104 of the rotation plate 103 and the upper surface of the intermediate portion 32.

Then, as shown in FIG. 10, the top plate 51 is lifted so that the metal core 71 recedes from the product P. At this time, the gas cylinder 61 and the gas cylinders 62, which are fixed to the top plate 51, are lifted together with the top plate 51. However, the piston rods of the gas cylinder 61 and the gas cylinders 62 are in the retracted state. Therefore, until the gas cylinder 61 and the gas cylinders 62 are released from the retracted state, the stripper backing 90 continues to be pressed through the coupling member 92 and the support rods 94. As a result, with the stripper backing 90 pressing the workpiece 200, the punch holder 80 is lifted together with the housing 52 and the top plate 51. Consequently, the metal core 71 recedes from the product P.

Then, as shown in FIG. 11, the top plate 51 is lifted until the upper surface of the punch holder 80 comes into contact with the opposing surface 104 of the rotation plate 103, that is, until the punch 70 returns to the preparation position, so that the punch 70 recedes from the product P. At this time, the stripper backing 90 is pressing the workpiece 200, and the support rods 94 are disposed between the stripper backing 90 and the switch member 100. Therefore, the switch member 100 will not move upward.

The holding pins 72 of the punch 70 are urged downward by the compression springs 73. When the punch 70 recedes from the product P, the holding pins 72 of the punch 70 project from the lower surface of the punch 70 and press the upper surface of the product P.

Although not shown in the drawings, the top plate 51 is lifted to separate the upper die assembly 50 from the lower die assembly 20 so that the product P is removed from the stamping apparatus 10. Accordingly, the lift-up mechanism 40 lifts the workpiece 200 upward in contact with the lower surface of the stripper backing 90.

At this time, the upper pins 81 move upward in accordance with the lifting of the upper die assembly 50. The intermediate portion 32, which is pressed by the upper pins 81 through the lower pins 24, is moved upward by the urging force of the gas cylinders 31 until the intermediate portion 32 comes into contact with the lower surface of the die plate 23. As a result, the pushing member 35 is moved upward to a position where the upper surface of the pushing member 35 is flush with the upper surface of the die 25. As described above, since the workpiece 200 is spaced apart from the product P by a slight gap in the vertical direction, the product P remains on the pushing member 35.

As described above, during the set period in which the punch 70 recedes from the bottom dead center to the preparation position, the delay device 120 delays lifting movement of the pushing member 35 in relation to receding movement of the punch 70. As a result, the upper die assembly 50 including the upper pins 81, the workpiece 200, and the product P are moved upward while maintaining the vertical position relative to each other.

Then, as shown in FIG. 12, when the upper die assembly 50 is further lifted, the holding pins 72 are lifted upward together with the punch 70, and the product P is lifted by the lifter 37 above the upper surface of the pushing member 35. When the product P is lifted by the lifter 37, the upper surface of the product P is pressed by the holding pins 72.

Finally, the upper die assembly 50 is further lifted, and the product P is removed outside from the pushing member 35.

As described above, the stamping apparatus 10 punches out the product P from the workpiece 200.

The operation and advantages of the present embodiment will now be described.

(1) The stamping apparatus 10 includes the die 25, the punch 70, the back-pressure device 30, the lift-up mechanism 40, and the delay device 120. The workpiece 200 is mounted on the die 25. The punch 70 is arranged to approach and recede from the die 25 and configured to punch out the produce P from the workpiece 200. The back-pressure device 30 includes the pushing member 35 disposed in the die 25 and urges the pushing member 35 toward the punch 70 so that back pressure is applied to the workpiece 200. The lift-up mechanism 40 is configured to lift the workpiece 200 above the die 25 when the punch 70 recedes from the die 25. The delay device 120 is configured to delay lifting movement of the pushing member 35 in relation to receding movement of the punch 70 when the punch 70 recedes from the die 25.

When punching out the product P from the workpiece 200 using the die 25 and the punch 70, the pushing member 35 disposed in the die 25 applies back pressure to the workpiece 200. This increases the processing accuracy of the product P.

However, when punching out the product P from the workpiece 200 all at once, the back-pressure device 30 may push the product P back to the punched hole in the workpiece 200 formed by the punching-out of the product P, which is so-called push-back. Occurrence of push-back is undesirable particularly when the product P has a number of teeth on the outer circumference.

In this regard, with the configuration described above, when the punch 70 recedes from the die 25, the lift-up mechanism 40 lifts the workpiece 200 above the die 25. In addition, the delay device 120 delays lifting movement of the pushing member 35 in relation to receding movement of the punch 70. As a result, the workpiece 200 is lifted while the product P, which is punched out from the workpiece 200, remains on the pushing member 35 in the die 25. Thus, even when the product P is punched out all at once from the workpiece 200, occurrence of push-back is limited. This improves the productivity of stamping.

(2) The back-pressure device 30 includes the gas cylinders 31 (urging portion) upwardly urging the pushing member 35 and the intermediate portion 32 disposed between the pushing member 35 and the gas cylinders 31. During the set period from when receding movement of the punch 70 starts, the delay device 120 restricts upward movement of the intermediate portion 32, thereby delaying lifting movement of the pushing member 35 in relation to the receding movement of the punch 70.

With this configuration, during the set period from when receding movement of the punch 70 starts, the delay device 120 restricts upward movement of the intermediate portion 32, which is disposed between the gas cylinders 31 and the pushing member 35, thereby delaying lifting movement of the pushing member 35 in relation to the receding movement of the punch 70. Thus, the delay device 120 is configured independently from the back-pressure device 30. This simplifies the structure of the back-pressure device 30.

The back-pressure device 30 is configured to urge the pushing member 35 using the gas cylinders 31. This dispenses with, for example, hydraulic control of a hydraulic cylinder.

(3) The delay device 120 includes the lower pins 24 and the upper pins 81. The lower ends of the lower pins 24 are opposed to the upper surface of the intermediate portion 32. The lower pins 24 are movable in the vertical direction. The lower ends of the upper pins 81 are configured to contact and separate from the upper ends of the lower pins 24. The upper pins 81 move together with the punch 70 in the vertical direction. The delay device 120 further includes the switch member 100 and the drive mechanism 110. While the switch member 100 moves together with the punch 70 in an approaching-receding direction of the punch 70, the switch member 100 does not lift or lower when the punch 70 is located between the bottom dead center and the preparation position, which is located above the bottom dead center. The drive mechanism 110 is configured to move the switch member 100. In the delay device 120, during a period in which the punch 70 is punching out the product P, the switch member 100 is set to the accommodated position, and during a period in which the punch 70 recedes from the bottom dead center to the preparation position, the switch member 100 is set to the opposing position. Thus, the upper pins 81 and the lower pins 24 are in contact with each other and held between the opposing surface 104 of the rotation plate 103 and the upper surface of the intermediate portion 32.

With this configuration, while the switch member 100 moves together with the punch 70 in the vertical direction, the switch member 100 does not lift or lower when the punch 70 is located between the bottom dead center and the preparation position, which is located above the bottom dead center.

While the punch 70 is punching out the product P, the switch member 100 is set to the accommodated position. This limits downward pressing of the upper surface of the intermediate portion 32 performed by the upper pins 81 and the lower pins 24, which are in contact with each other, thereby limiting shortage of back pressure applied to the workpiece 200.

During a period in which the punch 70 recedes from the bottom dead center to the preparation position, the switch member 100 is set to the opposing position. The upper pins 81 and the lower pins 24 are in contact with each other and held between the opposing surface 104 of the rotation plate 103 and the upper surface of the intermediate portion 32. Thus, during a period from when receding movement of the punch 70 starts at the bottom dead center until the punch 70 recedes to the preparation position, the intermediate portion 32 continues to be pressed downward by the upper pins 81 and the lower pins 24.

(4) The switch member 100 is rotational about the axis C extending in the vertical direction. The drive mechanism 110 rotates the switch member 100 about the axis C between the accommodated position and the opposing position.

This configuration reduces the space for moving the switch member as compared to, for example, a configuration including a switch member that slides in a direction orthogonal to the vertical direction to move between the accommodated position and the opposing position. This reduces the size of the stamping apparatus 10.

(5) The lifter 37 is disposed in the pushing member 35 and is urged toward the punch 70 so that the lifter 37 retractably extends from the pushing member 35 to lift the product P above the upper surface of the pushing member 35.

With this configuration, the product P is lifted above the upper surface of the pushing member 35. This limits close contact of the product P with the pushing member 35. As a result, the product P may be readily discharged.

Moreover, for example, when a protrusion is formed on the surface of the product P opposed to a pushing member, the upper surface of the pushing member will be provided with a recess for forming the protrusion or for receiving the protrusion. In this case, when the upper surface of the pushing member is lifted to the upper surface of the die 25, the protrusion of the product P is fitted in the recess in the pushing member. This hampers discharging of the product P.

In this regard, with the configuration described above, the lifter 37 disposed in the pushing member 35 lifts the product P, which is punched out from the workpiece 200, above the upper surface of the pushing member 35. This allows the protrusion of the product P to be released from the recess of the pushing member 35. Thus, the product P may be readily discharged.

(6) The holding pins 72 are disposed in the punch 70 to retractably extend from the punch 70 so when the product P is lifted by the lifter 37, the holding pins 72 press the upper surface of the product P and hold the position of the product P.

With this configuration, when the product P is lifted by the lifter 37, the holding pins 72 disposed in the punch 70 press the upper surface of the product P to hold the position of the product P. This also limits occurrence of push-back of the product P caused by the lifter 37.

(7) When the punch 70 recedes from the die 25, the workpiece 200 is lifted above the die 25, and the lifting movement of the pushing member 35 is delayed in relation to the receding movement of the punch 70.

The method obtains advantages corresponding to advantage (1) described above.

The present embodiment may be modified as follows. The present embodiment and the following modified examples can be combined as long as the combined modified examples remain technically consistent with each other.

The metal core 71 may be omitted.

The number and layout of the support pins 33 and the pressing pins 53 may be modified as necessary.

The number and layout of the holding pins 72 may be modified as necessary.

The holding pins 72 may be omitted.

The lifter 37 may be omitted. In this case, the product P remains on the upper surface of the pushing member 35.

The gear portion 112 of the slide bar 111 in the drive mechanism 110 may be configured separately from the slide bar 111. The gear portion 107 of the rotation plate 103 may be configured separately from the rotation plate 103.

The drive mechanism 110 may rotate the switch member 100 using an actuator other than the air cylinder 113 such as a servomotor or an electromagnetic solenoid.

The switch member 100 may slide in a direction orthogonal to the vertical direction to move between the accommodated position and the opposing position.

The number and layer of the upper pins 81 and the lower pins 24 may be modified as necessary.

The upper pins 81 do not necessarily have to be urged by the compression springs 82.

The delay device may restrict upward movement of the intermediate portion 32, for example, using pins that are integrally formed by the upper pins 81 and the lower pins 24. In this case, the pins may be disposed at opposite sides of the workpiece 200 in a width-wise direction that is orthogonal to both the vertical direction and the conveying direction X in order to avoid interference with the workpiece 200. In this case, the through holes 202 may be omitted from the workpiece 200.

The gas cylinders 31, 60, 61, and 62 may be hydraulic cylinders or pneumatic cylinders.

The back-pressure device 30 may drive the pushing member 35 using an actuator such as a ball screw so that the pushing member 35 vertically lifts and lowers to apply back pressure to the workpiece 200.

The range in application of the stamping apparatus 10 is not limited to the product P, which has gear teeth on the outer circumference. The stamping apparatus 10 of the present embodiment can be employed in producing products having various shapes as long as those are punched out of a plate-shaped workpiece.

Various changes in form and details may be made to the examples above without departing from the spirit and scope of the claims and their equivalents. The examples are for the sake of description only, and not for purposes of limitation. Descriptions of features in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if sequences are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined differently, and/or replaced or supplemented by other components or their equivalents. The scope of the disclosure is not defined by the detailed description, but by the claims and their equivalents. All variations within the scope of the claims and their equivalents are included in the disclosure. 

What is claimed is:
 1. A stamping apparatus, comprising: a die on which a workpiece is mounted; a punch arranged to approach and recede from the die and configured to punch out a product from the workpiece; a back-pressure device including a pushing member disposed in the die, the back-pressure device urging the pushing member toward the punch to apply back pressure to the workpiece; a lift-up mechanism configured to lift the workpiece above the die when the punch recedes from the die; and a delay device configured to delay lifting movement of the pushing member in relation to receding movement of the punch when the punch recedes from the die.
 2. The stamping apparatus according to claim 1, wherein the back-pressure device includes an urging portion that upwardly urges the pushing member and an intermediate portion disposed between the pushing member and the urging portion, and during a set period from when the receding movement of the punch starts, the delay device restricts upward movement of the intermediate portion to delay the lifting movement of the pushing member in relation to the receding movement of the punch.
 3. The stamping apparatus according to claim 2, wherein the urging portion includes a gas cylinder.
 4. The stamping apparatus according to claim 2, wherein the delay device includes a lower pin movable in an approaching-receding direction of the punch, the lower pin having a lower end opposed to an upper surface of the intermediate portion, an upper pin that moves together with the punch in the approaching-receding direction of the punch, the upper pin having a lower end configured to contact and separate from an upper end of the lower pin, a switch member including an opposing surface opposed to an upper end of the upper pin and a recess disposed in a portion of the opposing surface to accommodate the upper end of the upper pin, wherein while the switch member moves together with the punch in the approaching-receding direction of the punch, the switch member does not lift or lower when the punch is located between a bottom dead center and a set position that is located above the bottom dead center, and a drive mechanism configured to move the switch member between an accommodated position in which the upper end of the upper pin is accommodated in the recess and an opposing position in which the upper end of the upper pin is opposed to the opposing surface, while the punch is punching out the product, the switch member is set to the accommodated position, and while the punch is receding from the bottom dead center to the set position, the switch member is set to the opposing position, so that the upper pin and the lower pin are in contact with each other and held between the opposing surface and the upper surface of the intermediate portion.
 5. The stamping apparatus according to claim 4, wherein the switch member is rotational about an axis that extends in the approaching-receding direction of the punch, and the drive mechanism rotates the switch member about the axis between the accommodated position and the opposing position.
 6. The stamping apparatus according to claim 1, wherein a lifter is disposed in the pushing member and urged toward the punch to retractably extend from the pushing member, and the lifter is configured to lift the product above an upper surface of the pushing member.
 7. The stamping apparatus according to claim 6, wherein a holding pin is disposed in the punch to retractably extend from the punch so that when the product is lifted by the lifter, the holding pin presses an upper surface of the product to hold a position of the product.
 8. A stamping method, comprising: when punching out a product from a workpiece by causing a punch to approach and recede from a die on which the workpiece is mounted, applying back pressure to the workpiece from a side opposite to the punch using a pushing member; and when the punch recedes from the die, lifting the workpiece above the die and delaying lifting movement of the pushing member in relation to receding movement of the punch. 